The present invention relates to a coin detection means and method, and, more particularly, to a coin detection means that employs a derived time constant characteristic tau (.tau.) representative of the coin undergoing examination, for coin detection and discrimination purposes, and to the method of use thereof.
It will be appreciated that, throughout this application, the term "coin" may be employed to mean any coin (whether valid or counterfeit), token, slug, washer, or other item which might be used by an individual in an attempt to operate a coin-operated device or system. An "acceptable coin" is considered to be an authentic coin, token, or the like of the monetary system or systems in which or with which the coin-operated device or system is intended to operate and of a denomination which the device or system is intended selectively to receive and to treat as an item of value.
Over the years a number of coin detection, validation, and verification means and techniques have been developed and utilized. Among the more effective of such means and techniques have been coin validation systems that have utilized a pair of coils positioned in a face-to-face arrangement to detect certain performance characteristics of circuits of which the coils form a part and the changes that occur in such performance characteristics when coins of different values pass between the coils of the coil pair. The use in such systems of a pair of coils, as opposed to a single coil, was found to be necessary and/or desirable in almost all instances in order to minimize system dependency upon coin-to-coil distances. By placing a pair of coils in a face-to-face arrangement, and by requiring the coin to be examined to pass therebetween, such dependency and the overall sensitivity of such validation systems to variations in distance between the coin and a given coil could be minimized. However, the use of a pair of coils in such systems, as opposed to a single coil, has resulted in increased system costs, both in terms of additional components and the labor required to install and service such additional components.
Additionally, and for the most part, such systems have required the tuning of individual constructions thereof in order to achieve a relative uniformity of operational result from individual construction to individual construction since the effect upon the circuit performance characteristics of a coin passing between the pairs of coils of different individual constructions of a given system type has been found to vary from construction to construction due to variations in construction component values and parameters, many of which variations, though perhaps minor, are nonetheless unpredictable, at least to some degree. Such variations may typically include deviations from individual construction to individual construction in coil inductance, coil resistance, circuit capacitance, and power supplies, among other things. By employing some type of tuning or programming for such individual constructions during system manufacture, which tuning or programming adds further in component and labor costs, a relative uniformity in end result from individual construction to individual construction can be achieved. However, even with such tuning and/or programming during the manufacture of the individual constructions, there remains a possibility that component values may change over time or that the system may drift out of tune, resulting in subsequent performance problems at later times. Still further, with many validation systems of the type under discussion, it has been found necessary or desirable to employ multiple pairs of coils because of an inability to obtain sufficient information for coin validation purposes from a single pair of coils, which additional components result in still further costs in components and labor.
The coin detection means of the present invention is designed to eliminate or minimize the need for many of such additional components, and the labor associated therewith, yet to permit coin detection and validation to be accomplished by the use of only a single sensor coil instead of one or more pairs of sensor coils. As so designed and constructed, the coin detection means of the present invention operates to detect a coin, when it is within the field of the sensor coil, essentially independently of coin-to-coil distance, and with little or no need for tuning and/or individualized construction programming during an individual construction's manufacture, to permit a time constant characteristic of a detected coin to be derived through the utilization of a single sensor coil.